This excerpt from video released to the public shows the most complete version of the shooting of 17-year-old Laquan McDonald. It is edited for length by the Chicago Tribune. Warning: This video contains graphic images.

This excerpt from video released to the public shows the most complete version of the shooting of 17-year-old Laquan McDonald. It is edited for length by the Chicago Tribune. Warning: This video contains graphic images.

Alma Benitez had just stopped for a bite to eat at a Southwest Side Burger King in October 2014 when she witnessed the now-infamous killing of 17-year-old Laquan McDonald by a Chicago police officer.

Benitez, who was headed home from the night shift at a nearby sandwich shop, was adamant from the beginning that Officer Jason Van Dyke had no reason to fire at McDonald, who was shot 16 times, including numerous times as he lay wounded in the street.

But a federal lawsuit filed this week alleged Benitez was detained at a police station for hours and pressured to change her story by detectives who falsely claimed video of the shooting showed McDonald had lunged at officers with a knife, contradicting her account.

The dashboard camera video from a squad car at the scene, however, showed that Van Dyke opened fire as McDonald walked away with the knife in his hand, according to the lawsuit.

The suit also alleged a long-standing code of silence within the Police Department allowed officers to cover up details of the shooting and keep the dashcam video out of the public eye for more than a year.

A city Law Department spokesman declined to comment Thursday on Benitez's lawsuit, citing the pending litigation.

Van Dyke was charged last November with first-degree murder just hours before the court-ordered release of the video caused a firestorm of controversy that led to weeks of street protests, the firing of police Superintendent Garry McCarthy and a U.S. Justice Department investigation of Chicago police practices that is ongoing.

Benitez's lawsuit, filed Monday, marks the first by a witness to the McDonald shooting that alleges pressure by police to cover up Van Dyke's actions.

But in the weeks before the city agreed to pay $5 million to McDonald's estate, lawyers representing the teen's family alleged in a scathing letter to city attorneys that at least two other witnesses to the shooting in addition to Benitez were treated in similar fashion. All three were questioned for hours at the Area Central police headquarters and pressured into changing their accounts to match the official police version, according to the March 2015 letter.

Benitez testified last year before a federal grand jury investigating the shooting, according to multiple sources, but no criminal charges have been filed.

Speaking to reporters after an address at the City Club of Chicago this week, U.S. Attorney Zachary Fardon confirmed only that "there is and was a federal investigation related to" the McDonald shooting.

Meanwhile, a Cook County special prosecutor who has been appointed to probe a possible cover-up by other officers and supervisors at the scene is impaneling a grand jury.

The accounts of multiple officers at the scene differed sharply with what the video showed.

Benitez could not be reached for comment Thursday. Her lawyer, Amanda Yarusso, told the Tribune the 31-year-old mother of three was headed home at about 10 p.m. on Oct. 20, 2014, when she and a friend stopped at the Burger King drive-thru in the 4100 block of South Pulaski Road to get something to eat.

After McDonald was shot, Benitez was interviewed by television news crews at the scene and featured in several news reports the next day saying McDonald was clearly not a threat to the officer. She said Van Dyke had no reason to open fire.

"It was superexaggerated," Benitez said in one report aired on WMAQ-Ch.5. "You didn't need that many cops to begin with. They didn't need to shoot him. They didn't. They basically had him face to face. There was no purpose why they had to shoot him."

According to the lawsuit, Benitez had tried to take photos and video of the scene with her cellphone but wasn't sure the recordings worked. Once police "became aware" she was trying to record the incident, they demanded she surrender her phone and accompany officers to the detective headquarters at 51st Street and Wentworth Avenue, where she was detained for as long as six hours, the suit alleges.

The suit accuses several officers and detectives of then writing false reports misstating what Benitez and other witnesses at the scene had told them.

According to handwritten police reports released by the city in the weeks after Van Dyke was charged, Benitez told detectives she saw a black male running south on Pulaski being followed by a "lot of police." She tried to grab her phone and record the "chase" but wasn't sure she was able to record anything, according to the detective's account of what she told police. She then heard at least eight "continuous" shots and saw a police officer pointing a gun at the black male, who at that point was on the ground, the report stated.

The report stated Benitez allowed the detective to check her phone but that it was "negative for any video recording."

A handwritten note near the top of the report stated Benitez "refused to remain" at the Area Central headquarters "for further interview" and left with her friend.

Benitez, however, alleges in her lawsuit that she was never told she was free to go. Detectives kept her at the police station until about 4 a.m., when she was finally allowed to leave, she alleges.

According to the March 2015 letter from McDonald's family attorneys, Benitez reported she was "appalled by what she witnessed, and actually screamed out 'stop shooting!' as Officer Van Dyke continued to discharge his weapon while Laquan was laid in the street." The letter claimed she was allowed to leave the station only after she demanded to see a lawyer and that she was "threatened and harassed" on multiple occasions after she was featured in news reports.

Police reports noted another witness, a truck driver who was updating his logbook in the Burger King parking lot, said he heard shots but did not see the actual shooting. But the truck driver later told the McDonald family lawyers he had witnessed the shooting and told police in an interview at the area headquarters that it was "like an execution," according to a second letter sent to the city's deputy corporation counsel on March 23.

But officers on the scene reported a far different scene in their written accounts. At least one patrol officer said McDonald was advancing on the officers in a menacing way and swung his knife at them in an "aggressive, exaggerated manner" before he was fatally shot. Officers claimed, too, that even after McDonald had been shot by Van Dyke, the teen tried to lift himself off the street with the knife pointed toward the officers.

Detective David March ruled the shooting a justifiable homicide, saying McDonald had committed an aggravated assault against the three officers and forced Van Dyke to shoot "in defense of his life," according to the reports. March also found no discrepancies between the video and officers' statements, though city and law enforcement officials now acknowledge inconsistencies.

In August, 22 months after McDonald's shooting, police Superintendent Eddie Johnson moved to fire Van Dyke, three other patrol officers and a sergeant he accused of lying about the shooting.